Blood test detects tumor DNA to guide advanced cancer treatment

The study was led by Dr Chad Tang, Associate Professor of Radiation Oncology at The University of Texas MD Anderson Cancer Center, Houston, USA, and presented by Dr Alex D Sherry, Assistant Professor of Radiation Oncology at The Mayo Clinic, Rochester, USA. It is also published today in the Journal of Clinical Oncology.

Dr Sherry told the Congress: "Multiple studies have suggested that treating oligometastatic cancer with a combination of both chemotherapy and local treatments directed at the site of tumors, such as high-precision radiotherapy, may improve cancer control. But counting lesions might not be the most effective way of identifying which patients might benefit from radiotherapy."

Dr. Chad Tang, Associate Professor of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USAWe wanted to investigate whether a new test that measures circulating tumor DNA - parts of the tumor that are shed into the bloodstream - would help us work out which patients would benefit the most from combining chemotherapy with radiation therapy, predict their response to therapy and give them a more accurate long-term prognosis."

The trial included 237 patients in six sub-groups (a group of patients with pancreatic cancer, one with breast cancer, one with kidney cancer, two prostate cancer groups receiving different hormone therapy schedules, and a final group of patients with any other type of cancer) who each had between one and five metastases. These patients were then randomly chosen to receive either drug therapy alone or drug therapy combined with radiation therapy.

Patients' blood was collected at the start of the trial, after three months, and again when their cancer had spread, and tested for the presence of circulating tumor DNA (ctDNA).

Dr Sherry and Dr Tang's team found that patients who had tumor DNA in their blood at the start of the trial were more likely to experience continued cancer growth and were more likely to die.

They also found that those patients who had radiation therapy directed at sites of cancer spread (alongside the drug therapy) experienced improved clearance of ctDNA.

The team hope that testing for ctDNA may help determine which patients could be the best candidates for radiotherapy and may also help refine therapy by letting doctors know if and when a cancer has changed and developed resistance to current treatment.

Dr Sherry adds: "We hope that future studies will evaluate whether systemic therapy should be changed in those patients and whether ctDNA can be used to help distinguish which sites of cancer are responding to treatment versus becoming resistant."

ESTRO President, Professor Matthias Guckenberger, from University Hospital Zurich, Switzerland, who was not involved in the research said: "More and more research is showing that treating patients with a limited spread of cancer with both drug therapy and high-precision radiotherapy can improve their chances of survival. This study – one of the largest carried out in this patient group – suggests that by adding a blood test we can also monitor and target patients' radiotherapy treatment much more effectively.

"The non-invasive ctDNA marker test could support established imaging techniques, providing a more refined way of checking how patients' cancer has spread and helping doctors to determine how and when radiotherapy should be used to treat it.

"Using ctDNA as a marker could also help tailor treatment where therapy might not be working as effectively, and offer additional reassurance where treatment is successful."

Source:

European Society for Radiotherapy and Oncology (ESTRO)

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